1. Field of the Invention
The present invention relates to an exposure apparatus and device manufacturing method used to manufacture a device such as a semiconductor device.
2. Description of the Related Art
A method of sensing a mark and a method of calculating a shot arrangement on a substrate in a conventional semiconductor manufacturing exposure apparatus will be described with reference to FIG. 12 (Japanese Patent Laid-Open No. 2005-294474).
First, an illumination condition switching unit 4 selects an illumination condition suitable for observing an alignment mark. A stage driving unit 17 moves a stage to a position where it is possible to observe an alignment mark (to be referred to as a “mark” hereinafter) WM on a substrate W. An illumination unit 3 is turned on to illuminate the mark WM through an imaging optical system 5, beam splitter 7, reticle R, and projection optical system 1. FIG. 3A shows an example of the mark WM in which a plurality of patterns having the same shape are arranged. A light beam reflected by the mark area passes through the projection optical system 1 and reticle R and reaches the beam splitter 7. The beam splitter 7 reflects the light beam so that the image of the mark WM is formed on the imaging plane of an image sensing unit 8 through an imaging optical system 6. The image sensing unit 8 photoelectrically converts the mark image. The illumination unit 3, illumination condition switching unit 4, imaging optical systems 5 and 6, beam splitter 7, and image sensing unit 8 form a mark image sensing optical system 2.
Next, an A/D converter 9 converts the mark image into a two-dimensional digital signal sequence. The digital signal sequence converted by the A/D converter 9 is sent to a control unit (a controller) 10′. The control unit 10′ includes a detection condition switching unit 12′, calculation unit 13′, and generation unit 14′. The generation unit 14′ generates a plurality of sample shot sets each including at least two of a plurality of shot areas by using the converted digital signal sequence. A measuring device (not shown) measures the central position of the mark WM. Before the measurement, the detection condition switching unit 12′ selects a detection condition suitable for mark measurement.
As shown in FIG. 4, N shot areas S1, S2, . . . , Si, . . . , SN exist on the substrate W. Each of the N shot areas has the mark WM. A sample shot set including, as sample shots, a plurality of appropriate shot areas indicated by, for example, hatching in FIG. 4 of the N shot areas on the substrate W is determined in advance. The measuring device measures the mark WM of each sample shot included in the set sample shot set. The calculation unit 13′ calculates the shot arrangement on the substrate by executing a statistical process of the measurement results of the mark WM by a stage position detection unit 18 and the measuring device.
The shot arrangement calculation method is effective in calculating an accurate shot arrangement. Conventionally, however, the operator determines the illumination light wavelength corresponding to a stable mark shape in the substrate W or executes inspection by using an overlay inspection apparatus different from the exposure apparatus, thereby determining the measurement condition suitable for shot arrangement calculation.